Update: It appears that many/most Apple TVs are still not seeing the 4.4.1 update, although Jeff Gamet reports he's spotted it in the wild. Mike Rose reported that he installed 4.4.1 Tuesday night via a tethered restore (USB connection) from iTunes, but that it took several tries to successfully download the 370MB OS package. If you're not seeing the update yet, try again later on today.
Last week, Apple update the Apple TV to version 4.4, adding the long-awaited AirPlay mirroring features. Now it has rolled out an incremental version (4.4.1) that adds some minor bug fixes and tweaks. This 4.4.1 version was initially released today, October 18, and then pulled after reports of bricked Apple TV units surfaced. The problem with this update was fixed and Apple has made it publicly available again.
This 4.4.1 version may be small, but it builds on the 4.4 firmware update which added several new features to the Apple TV. With 4.4, you can use AirPlay mirroring with your iPad 2 and iPhone 4S and view PhotoStream content that's stored in iCloud. Apple TV owners can also watch movie trailers as well as new content from the NHL and Wall Street Journal Live.
Some AppleTV owners had trouble updating to the 4.4 version without doing a full restore or tethering to iTunes. The 4.4.1 version should clear up those issues.